1. Field of the Invention
The invention relates to a device for the mechanical cleansing of fluids, especially of a cooling water to be supplied to a heat exchanger, with a rotationally symmetrical filter body arranged within the cooling water feeding pipe and a suction device on the same axis partially acting upon the windward filter surface, and, which is rotatably arranged in such a manner that it crosses the complete filter surface.
2. Description of the Related Art
A device of this kind is known for example from DE-PS 33 47 064 and DE-OS 34 19 698. The suction device consists therein usually of a slot-shaped radially running nozzle, which is rotationally driven and which crosses the inner surface of the filter and is connected to a suction pipe leading outwards. In order to remove deposits on the filter windward of the cool water flow, diminished pressure is produced therein in the suction nozzle by the connection of the suction pipe to a space at low pressure, by which means a back-flow from the outside of the filter is produced in each region of the filter surface to be cleansed, with which the impurities are to be carried away. This back-flow through the filter from the outside to the inside takes place however only if the edges of the suction nozzle are led along the filter surface with a relatively small gap. The suction nozzle is therefore usually provided with flexible sealing lips, which slide along the filter surface. However, the danger exists that deposits of greater volume, such as stones or pieces of wood, are not gripped by the nozzle but are pushed on the filter surface in front of the nozzle. It is therefore customary to form the foward sealing lip of the nozzle somethat smaller in the direction of rotation and with a gap from the filter surface and simply to allow the rear sealing lip to slide along the filter surface. By this means, larger sediments on the filter surface are picked up by the nozzle; yet, a considerable amount of cooling water windward of the filter body streams sideways into the nozzle, so that the desired back-flow through the filter body is itself strongly reduced or completely cancelled, so that the suction effect is considerably reduced. Attempts have been made to reduce this disadvantage by arranging a spray nozzle rotating with the suction nozzle on the leeward side of the filter body, which yields the desired back-flow. Such an additional arrangement is however, very expensive and of limited effect.